Hydrophilic or soft contact lenses are mainly produced from water-absorbable plastic materials such as 2-hydroxyethylmethacrylate (HEMA) which may be crosslinked with a tetra-functional monomer such as ethylene glycol dimethacrylate as disclosed in U.S. Pat. No. 3,988,274.
Attempts have been made to color such soft contact lenses for the purpose of enhancing the aesthetic beauty of the eye of the wearer of the colored lens. One prior art technique is to paint or print a colored portion onto a soft contact lens using an implement such as a brush, as disclosed in Contact Lens Forum, Volume 3, No. 8, Aug., 1978, page 89. Another technique involves the cementing of a colored covering layer onto a clear hydrogel lens as disclosed in U.S. Pat. No. 3,679,504. According to these techniques, the entire surface of the contact lens is colored. This is a disadvantage since the coloring material separates from the lens during use and is not sufficiently gas permeable.
In order to overcome these disadvantages, a number of prior art techniques have been developed. According to these prior art techniques the colored soft contact lens is manufactured with a clear center portion so as not to obstruct the vision of the wearer. For example, U.S. Pat. No. 3,679,504 discloses a method of producing a colored soft contact lens having a clear center portion surrounded by a colored portion. According to the patent, a thin covering layer of hydrogel is first formed, whereupon coloring is applied to the covering layer. The colored covering layer is then joined by a monomer cement to the concave face of an existing soft lens. The coloring may be applied such that the central lens portion is left clear.
U.S. Pat. No. 3,962,505 also discloses a colored soft contact lens with a clear central portion. The patent discloses a method of making a contact lens having an annular colored ring concentric with a clear central portion. According to the method, a cylindrical well is cut in a plastic block, and an annular ring which may be colored, is disposed in the well. The portion of the well above the ring is subsequently sealed by cementing a plug therein. The desired lens shape is then cut from the plastic block to yield a lens having a colored annular ring.
U.S. Pat. No. 4,157,892 is also directed to a colored soft contact lens having a clear central portion.
While these prior art techniques for producing colored soft contact lenses having a clear central portion overcome the disadvantage possessed by the prior art techniques which color the entire surface of the soft contact lens, the manufacturing processes for producing these improved colored soft contact lenses are complicated and expensive.
Applicant has overcome these disadvantages by producing a colored soft lens with a clear central portion by a simple method which results in a colored soft contact lens which is structurally different from the colored soft contact lenses disclosed in the prior art.